A growing trend is to power locomotives with less expensive, cleaner burning gaseous fuels, such as natural gas. However, even though locomotives are large vehicles, they typically have limited space available for the storage of such gaseous fuels due to the placement of various on-board power equipment, such as the engine, electrical generator, and the like. This situation is exacerbated with gaseous fuels such as natural gas, because even when stored as a cryogenic liquid, such fuels have substantially lower energy density than liquid fuels, such as diesel. Thus, these gaseous fuels (e.g., natural gas) typically require much larger storage tanks than liquid fuels (e.g., diesel) in order to produce the same refueling range. In addition, in systems where the alternative gaseous fuel is designed to burn in combination with the existing liquid fuel, then storage tanks for both fuels must be accommodated in the already-constrained space.
In order to improve the energy density of gaseous fuels, the gaseous fuel is commonly compressed for storage, often to pressures of several thousand pounds per square inch. Thus, the storage tanks containing these fuels are typically structurally reinforced pressure vessels, and the fuel lines and valves that deliver the fuel are typically exposed to this elevated tank pressure. In addition, the locomotive may experience significant shock and vibratory loading due to its operating environment, and may also experience significant environmental fluctuations, such as extreme changes in temperature. As such, the system for securing the fuel tanks and fuel delivery system should be able to withstand such loading and environmental variations over the multi-decade life of the locomotive. Also due to these severe operating conditions, the storage tanks, fuel lines, and other components are usually governed by regulations that mandate regular inspection and maintenance. However, in a complex, multi-tank, multi-line system, the ability to conveniently and thoroughly inspect such components is often hindered by difficult access to the components.
One known method for facilitating the storage and delivery of gaseous fuels includes the use of “tender cars,” which carry the gaseous fuel supply in a separate train car that forms part of the train consist. The tender car is typically located adjacent to the locomotive and is fluidly connected to the locomotive for supplying gaseous fuel to the engine. However, in the United States, current regulations require that the storage of all liquid and/or gaseous fuels must be on-board the locomotive during operation, and thus current regulations prohibit the use of such tender cars. Even if such regulations were changed to permit tender cars, the tender cars present significant logistical problems for the operator, in that, one or more of these additional tender cars must always be coupled to the locomotive during transit. In many short line, switching and industrial locomotive operations, the train length is at a premium, and the addition of another rail car within the train consist solely for the purpose of locomotive fuel supply may significantly inhibit effective operation of the rail line.